Day 1023

Monday.


1512.03538
The inner structure of dwarf sized haloes in warm and cold dark matter cosmologies
Gonzalez-Samaniego, Avila-Reese, Colin

By means of N-body+hydro zoom-in sims, study the evolution of the inner DM and stellar mass distributions of central dwarf galaxies formed in haloes of viral masses 2-3e10 Msun at z=0, both in a WDM and CDM cosmology.  The half-mode mass in the WDM power spectrum of the simulations is Mv=2e10 Msun.  In the DM only sims halo density profiles are well described by the NFW parametric fit in both cosmologies, though the WDM haloes have concentrations lower by factors 1.5-2.0 than their CDM counterparts.  In the hydro sims, the effects of baryons significantly flatten the inner density, velocity dispersion, and pseudo phase-space density profiles of the WDM haloes but not of the CDM ones.  The density slope measured at ~0.02xRv, alpha, becomes shallow in periods of 2 to 5 Gyr in the WDM runs.  Explore whether this flattening process correlates with the global SF, Ms/Mv ratio, gas outflow, and internal specific angular momentum histories.  Do not find any clear trends but when alpha is shallower than -0.5, Ms/Mv is always between 0.25 and 1%.  Conclude that the main reason of the formation of the shallow core is the presence of strong gas mass fluctuations inside the inner halo, which are consequence of the feedback driven by a very bursty and sustained SF history in shallow gravitational potentials.  The WDM halos, which ensemble late and are less concentrated than the CDM ones, obey these conditions.  There are also (rare) CDM systems with extend mass assembly histories that obey these conditions and form indeed shallow cores.  The dynamical heating and expansion processes, behind the DM core flattening, apply also to the stars in such a way that the stellar age and metallicity gradients of the dwarfs are softened, their stellar half-mass radii strongly grow with time, and their central surface densities decrease.


1512.03625
RCSLenS: A new estimator for large-scale galaxy-matter correlations
Buddendiek, et al

Measurements of galaxy bias b and galaxy-matter cross-correlation coefficient r for the BOSS LOWZ LRG sample.  Using a statistical WL analysis of the RCSLenS, find the bias properties of this sample to be higher than previously reported with b=2.45 and r=1.64 on scales between 3' and 20'.  Repeat the measurement for angular scales of 20'<theta<70' , which yields b=2.39 and r=1.24.  This is the first application of a data compression analysis using a complete set of discrete estimators for gg lensing and galaxy clustering.  As cosmo data sets grow, this new method of data compression will become increasingly important in order to interpret joint WL and galaxy clustering measurements and to estimate the data covariance.  In future studies this formalism can be used as a tool to study the LSS of the universe to yield a precise determination of cosmo parameters.


1512.03626
CFHTLenS and RCSLenS: Testing photometric redshift distributions using angular cross-correlations with spectroscopic galaxy surveys
Choi et al

Determine the accuracy of galaxy redshift distributions as estimated from photo-z probability distributions p(z).  The method utilizes measurements of the angular cross-correlation between photometric galaxies and an overlapping sample of galaxies with spectroscopic redshifts.  Describe the redshift leakage from a galaxy photometric redshift bin j into a spectroscopic redshift bin i using the sum of the p(z) for the galaxies residing in bin j. Then predict the angular cross-correlation between photo and spectra galaxies due to intrinsic galaxy clustering when i!=j as a function of the measured angular cross-correlation when i=j.  Also account for enhanced clustering arising from lensing magnification using a halo model.  The comparison of this prediction with the measured signal provides a consistency check on the validity of using the summed p(z) to determine galaxy redshift distributions in cosmo analyses, as advocated by CFHTLenS.  Present an analysis of the photo-z measured by CFHTLenS, which overlaps BOSS.  Also analyse RCSLenS, which overlaps both BOSS and WiggleZ Dark Energy Survey.  Find that the summed p(z) from both surveys are generally biased with respect to the true underlying distributions.  If uncounted for, this bias would lead to errors in cosmo parameter estimation from CFHTLenS by less than ~4%.  For photo-z bins which spatially overlap in 3-D with the spec-z sample, determine redshift bias corrections which can be used in future cosmo analyses that rely on accurate galaxy redshift distributions.


1512.03627
RCSLenS: Cosmic distances from weak lensing
Kitching, et al

Present results of applying the shear-ratio methods to the RCSLenS data.  The method takes the ratio of the mean of the WL tangential shear signal about galaxy clusters, averaged over all clusters of the same redshift, in multiple background redshift inns.  In taking a ratio the mass-dependence of the shear signal is cancelled-out leaving a statistic that is dependent on the geometric part of the lensing kernel only.  Apply this method to 535 clusters and measure a cocmo-indpendent distance-redshift relation to redshifts z~1.  In combination with Planck data, the method lifts the degeneracies in the CMB measurements, resulting in cosmo parameter constraints of OmegaM=0.31±0.10 and w0=-1.02±0.37, for a flat wCDM cosmology.